Author Topic: CPC 464 cost down IC117 IC118 upgrade?  (Read 1934 times)

0 Members and 1 Guest are viewing this topic.

Offline Yrouel

  • CPC464
  • **
  • Posts: 18
  • Country: it
  • Liked: 7
  • Likes Given: 1
CPC 464 cost down IC117 IC118 upgrade?
« on: 13:10, 06 May 15 »
Hello I noticed the unpopulated IC117 and IC118 in my CPC 464 rev. 4 cost down, what where they meant for? Is there any upgrade possible installing those chips (which ones are supposed to be?)

Offline gerald

  • Supporter
  • 6128 Plus
  • *
  • Posts: 1.557
  • Liked: 1111
  • Likes Given: 265
Re: CPC 464 cost down IC117 IC118 upgrade?
« Reply #1 on: 13:28, 06 May 15 »
Hi Lucky guy  ;)

IC117/118 are place holder to use 2 64k x 4 bit ram (km41464) instead of 8 64k x 1 bit (km4161).
Populating them will not give you more RAM as such.

However, it should be possible to get 128k by:
  - configuring the ASIC to be in 6128 mode
  - populate IC117/118
  - connect they CAS signal to ASIC NCAS1 intead of NCAS0 with a 33 ohm serie resistor . This mean having the CAS pin not soldered on PCB.
Note that I did not try that myself.

Info on configuring the ASIC can be found there : Arnold4 - CPCWiki
ASIC pinout can be found here : Gate Array and ASIC Pin-Outs - CPCWiki
Schematic of 6128 cost down in http://www.cpcwiki.eu/manuals/Amendment%20Service%20Manual.rar
There is no 464 cost down schematic

Offline dragon

  • 6128 Plus
  • ******
  • Posts: 1.540
  • Country: es
  • Liked: 689
  • Likes Given: 499
Re: CPC 464 cost down IC117 IC118 upgrade?
« Reply #2 on: 19:05, 06 May 15 »
what interesting i not know the arnold 4 page in cpc wiki. ¿So my cost down have signals to use the data separator?(mine is 6128).



¿The asic send signals in pins 35 and 36 or are dead?

Offline gerald

  • Supporter
  • 6128 Plus
  • *
  • Posts: 1.557
  • Liked: 1111
  • Likes Given: 265
Re: CPC 464 cost down IC117 IC118 upgrade?
« Reply #3 on: 19:18, 06 May 15 »
what interesting i not know the arnold 4 page in cpc wiki. ¿So my cost down have signals to use the data separator?(mine is 6128).



¿The asic send signals in pins 35 and 36 or are dead?
I guess that if there is an internal data separator, amstrad disabled it to not have a conflict if the external one.
Since all CPC/Plus are shipped with an external one, a good assumption is that the internal does not work at best. Maybe they planned one, but never designed it.

Offline dragon

  • 6128 Plus
  • ******
  • Posts: 1.540
  • Country: es
  • Liked: 689
  • Likes Given: 499
Re: CPC 464 cost down IC117 IC118 upgrade?
« Reply #4 on: 19:36, 06 May 15 »
mmm, I not 100% sure, maybe it work. Maybe the problem is the space in the asic of the plus. I mean maybe really not  is a problem type of designing a working data separator in the plus, but maybe a problem to fit it  in the asic space.

i remember read someone from amstrad  tell the asic used arond the 90% of  logic gates in the plus and they  not have more space to fit more things.

The other things amstrad design (the alternative ram space or the gate arrrays).works, Maybe their  planning is used it in the 6128/464, but first amstrad needs put the remaining stock of the data separator in the motherboards. And later it drop the idea a cause of space in the asic.(And then cpc classic is discountinued).

Who knows the truth :).

Offline Shining

  • Supporter
  • 464 Plus
  • *
  • Posts: 317
  • Country: de
    • Shinings little CPC page
  • Liked: 446
  • Likes Given: 218
Re: CPC 464 cost down IC117 IC118 upgrade?
« Reply #5 on: 23:34, 06 May 15 »
In the plus spec, there is written the following:
Quote
Floppy disc data separator: Because of timescale pressures, the data separator design in the ASIC has been deleted rather than improved .  Thus all models with a disk drive use an external SED9420 data separator.

Arnold V specs - CPCWiki

So perhaps this is the truth also for the cost-down...
TGS is back

Download my productions at:
cpc.scifinet.org

Offline dragon

  • 6128 Plus
  • ******
  • Posts: 1.540
  • Country: es
  • Liked: 689
  • Likes Given: 499
Re: CPC 464 cost down IC117 IC118 upgrade?
« Reply #6 on: 02:04, 07 May 15 »
Yeah, but is not explícit in details. Improved means they have a desing  built in the anterior asic.

But timescale preasures can be read  in two directions ,the diretion of not time to desing  the data separator working in the paper. And the direcction of you have a data separator working desing in the paper, but you not have time to implementated it in the new asic.

For example the design in the gate array 40007, is totally diferent at the design in 40008. They have the same functions, but the tecnology inside the chip is totally diferent. The same can happend between pre-asic and asic. Or  simply the data separator never work.

In the beginig of Arnold v document they tell the objetive is redesigning the asic. They probably speak about the pre-asic. We called it presasic, but is a  asic.
« Last Edit: 02:34, 07 May 15 by dragon »

Offline Yrouel

  • CPC464
  • **
  • Posts: 18
  • Country: it
  • Liked: 7
  • Likes Given: 1
Re: CPC 464 cost down IC117 IC118 upgrade?
« Reply #7 on: 17:45, 08 May 15 »
IC117/118 are place holder to use 2 64k x 4 bit ram (km41464) instead of 8 64k x 1 bit (km4161).
...
it should be possible to get 128k by:
  - configuring the ASIC to be in 6128 mode
  - populate IC117/118
  - connect they CAS signal to ASIC NCAS1 intead of NCAS0 with a 33 ohm serie resistor . This mean having the CAS pin not soldered on PCB.
Note that I did not try that myself.


Thanks, I ordered the ram chips but I still haven't decided if I'll modify the board or not. The board is pristine and if it was just a matter of soldering the new chips I wouldn't have any problem (I did that on my Atari 520STfm) but this mod involves basically bodge wires so it won't look so nicely so I have to think about it.